Several different approaches have been used in the scientific and technical literature to catalogue and compare all presently available mass spectrometry instrumentation technologies. At the most basic level, mass spectrometers can be differentiated based on whether trapping or storage of ions is required to enable mass separation and analysis. Non-trapping mass spectrometers do not trap or store ions, and ion densities do not accumulate or build up inside the device prior to mass separation and analysis. Common examples in this class are quadrupole mass filters and magnetic sector mass spectrometers in which a high power dynamic electric field or a high power magnetic field, respectively, are used to selectively stabilize the trajectories of ion beams of a single mass-to-charge (M/q) ratio. Trapping spectrometers can be subdivided into two subcategories: Dynamic Traps, such as for example the quadrupole ion traps (QIT) of Paul's design, and Static Traps, such as the electrostatic confinement traps more recently developed. Electrostatic traps that are presently available, and used for mass spectrometry, rely on harmonic potential trapping wells to ensure ion energy independent oscillations within the trap with oscillation periods related only to the mass to charge ratio of the ions. Mass analysis in some of the modern electrostatic traps has been performed through (i) use of remote, inductive pick up and sensing electronics and Fast Fourier Transform (FFT) spectral deconvolution. Alternatively, ions have been extracted, at any instant, by the rapid switching off of the high voltage trapping potentials. All ions then escape, and their mass-to-charge ratios are determined through time of flight analysis (TOFMS). Some recent developments have combined the trapping of ions with both dynamic (pseudo) and electrostatic potential fields within cylindrical trap designs. Quadrupole radial confinement fields are used to constrain ion trajectories in a radial direction while electrostatic potentials wells are used to confine ions in the axial direction with substantially harmonic oscillatory motions. Resonant excitation of the ion motion in the axial direction is then used to effect mass-selective ion ejection.